Ophthalmic lens



Feb. 12-, 1924; 1,483,727

H. w. HILL OPHTHALMIC LENS Filed Sept. 16. 1 919 FIGII FIGJII FIGSH FIGSZII INVENTOR. HARRY W HILL BY Y ATTORNEYS.

Patented Feb. 12, 1924.

um'reo sures ,PATENT OFF-ICE.

HARRY W. HILL, OF SOUTHIBRIDGE, MASSACHUSETTS, ASSIGNOB TO AMERICAN OPTI- CAL COMPANY, OF BOUTHBRIDGE, MASSACHUSETTS, A VOLUNTARY ASSOCIATION OF MASSACHUSETTS.

OPHTHALMIC LENS.

Application filed September- 18, 1919. Serial No. 824,087.

To all whom it may concern:

Be it "known that I, HARRY W. HILL, a citizen of the United States, residing at Southbridge, in the county of Worcester and State of Massachusetts, have invented certain new and useful Improvements in Ophthalmic Lenses, of which the following is a specification.

' This invention relates to improvements W in opthahnic lenses and has particular reference to an improved process for forming such lenses.

A large proportion of ophthalmic lenses are sold in semi-finished condition, that is,

w the manufacturer grinds'a power curve on one side of the blank, leaving the other side unground. The dispensing Optician grinds the other side to a curve that in combination with the first curve will give the required prescription. It is important, therefore, that before he does any work of grinding the second side the dispensing optician should how whether or not there are defects such as striae, bubbles, cracks, etc., in

535 the blank which cannot be removed when the second side is ground. If he does not detect these defects the finished lens will be worthless, and he will have thrown awa all! his work and the costthereof, and wi l 1 have to grind another all-over again, causing delay to the patient, etc. If both surfaces of the blank are cleared these defects may be readily detected by inspection, sim-' ply by holding them up to the *light and 8 looking through them. ff

lit is important that the unfinished side be cleared before the power curve side of the blank is ground as there would be a likelihood of injuring the power curve side M if the clearing were done afterwards. I,

therefore, provide cleared blanks for inspection and a process of making them in large numbers at once and before any grinding is done upon them.

56 Prior to my invention, in the production of ophthalmic lenses, it has been customa first to mould a lum of glass into a bla of concavo-convex orm, and after such moulding to grind and polish the resultant glass blank into a finished lens; that is to say, into a final completed prescri tion lens or into a lens blank finished in nal'form on one side and polished to produce transparency though requiring subsequent grind- 1n si c. This grinding and polishing of the second side of the lens blank, when the glass is to be-sold in the form of a blank, is

practically necessary in the case of bifocal lenses made from a single piece of glass or of other; lenses of high quality which must be inspected through the glass for defects of material ormanufacture before the article is placed on sale. This grinding and polishing of the second side is an expensive proposition to the manufacturer as, on account of the short radius of. curvature of the surfaces or their strong power, as it may be termed, and the size of the pieces of glass, the grinding and olishing must be done either as an individual job or at the most upon only two or three pieces at a t1me.

In addition, in the grinding of bifocal lenses for example from the molded glass, it is necessary to remove a considerable amount of stockfrom the molded blank relatively before all trace of pits and the like produced by molding may be removed, and since this type of grindin is a difi'erent operation requiring consi erable skill properly to produce the'surfaces, this too adds considerably to the cost of manufacture.

It is also a great saving in grinding to mold the blank substantially to the curve that is to be ground on the first surface or power curve side of the blank. As is Well known, molding mars and clouds the surface of the glass; hence ll bend or mold the blanks overa form on the side on which the first power curve is to be ground, leaving the other side cleared; hence when. the first side is ground and polished to curve the blankwill have both surfaces cleared.

It is, therefore, the object of the resent invention to eliminate these di culties which have been experienced in the prior art production of lenses and to provide a novel and improved process through the use of which lenses of the most perfect form or forms and ordinarily quite diificult and expensive to manufacture may be roduced more rapidly and inexpensively, an cleared blanks therefor which ma be made in large numbers at once, rea ily dropped to of prescription curve on the opposite r apparent to those skille form and adaptable for use and ready inspection.

7 Other purposes and advantages resultant from my improved rocess should be in the art by a reference to the following specification taken in connection with the accompanying drawings, and it will be understood that I may make an modifications in the. specific features hereinafter described within the scope of the appended claims without departing from or exceeding the spirit of my invention.

Figure I represents a view diagrammatically illustrating the condition of an ordinary molded blank.

Figure II represents this blank at the completion of certain steps of my process.

Figure III illustrates a further step of the process.

Figure IV illustrates another step therein.

Figure V illustrates a slight modification -of the features illustrated in connection with Figure III.

Figure VI illustrates from Figure V.

Figure VII illustrates the manner in which my blanks may be prepared, and

Figure VIII illustrates a prior art method.

the blank produced As mentioned in the preamble to my specification, in the rior art it has been custom; ary to mold lanks into concavo-conveX form, such as the shape of the glass blank 1 shown in Figure III of the drawings, this blank having been forced into this form while in semi-molten condition in suitable molds. The disadvantage at present inthis process of manufacturing the lenses is that, as is more clearly illustrated in connection wlth Figure I, when a blank I is produced by molding, the surfaces 2 and 3 of the blank are quite rough or pitted due to contact with the mold, and this necessitates considerable grlnding and labor before the surface is in finally usable condition- While this is not a ser1ou's matter in the man ufacture of ordinary spectacle or eye lass lenses having weak curves or curves 0% long radius, it becomes a more serious matter in the case of lenses of higher powers, or in other words of shorter radius, and particularly in the case of torics or similar lenses requiring more particular grinding operations properly to produce their surfaces, and is most important in connection with the manufacture of bifocal lenses due to the fact that these lensesare ordinarily produced from blanks of quite large diameter and of relatively strong curve. These combined features make it impossible at one time to surface, grind, or olish more than two or three of thezabla s as when finishing up the non- 1 side it is necessary to grind indithe removable center section vidually the bifocal surface of the glass. This Wlll possibly be best understood by reference to prior art view Figure VIII show- II. In-accomber of blanks may be ground in ordinary\ 8 plano grinding machines as indicated for example in Figure VII, so that in place of being an individual proposition, large numbers if blanks may be simultaneously produce Having thus produced these blanks I drop them by heat softening on suitable molds 4, this softening being sufficient to allow the glass to'bend under its own weight but without being reduced to a molten or truly plastic condition, with the result that the upper surface 2 maintains its polished condition, while when the rocess is properly conducted, the lower sur ace 3 will show but slight variation from its former polished condition due to contact with the mold. Consequently, but slight work is required to restore the polish on this surface. In this way it is possible to produce a toric curve, for example,

on thesurface 3, or a bifocal curve comprising the distance portion 5 and reading portion 6, or various types of deformed surfaces may be thus pro need, and in many instances it will be found that surfaces thus produced require only polishing as by paration of the semi-finished lens blank. This semi finished lens blank, on account of the previous polishing of the surface 2, will be entirely transparent to vision, so that the condition of the glass may be readily determined before itis placed on the market.

It will be noted that in Figure V I have shown the production of a blank for bifocal lenses, this form having 9 which may be interchanged to produce various reading portion curves '6 in connection with the samedistance curve 5.

In the event that there is any roughness the mold 8 with a polisher 7 to complete the preor clouding of the surface 3 of bifocal. surfaces 5 and 6 due to the drop ing of the blank, I may then grind an polish or smooth and polish this surface or these surfaces in the carrying out of my process, but in lace of having to remove the pronounced roughness from molding as customa in the prior art forms there is but a slig t amount of glass that must be removed or given surface flow to produce the necessary polish, so that a considerable saving in manufacturing cost is effected through tion of glass in flat sheet'form, forming a mold with a major or distance curve portion and a projecting center curve portion, placing the blank supported on the center curve portion and subjecting the mold and blank to gradual heat to cause the blank to sub-- side onto the mold, substantially as illustrated.

2. The process of producing a blank for a bifocal lens consisting in polishing a portion of glass in'a single continuous surface, forming a mold with a major'portion having the complement of the curve desired on the distance vision portion of a bifocal and a central minor curve portion, supporting theblank on the minor curve, portion and mold, substantially as illustrated.

subjecting the mold and blank to gradual heat to cause the blank to subside onto the 3. The process of producing a blank for a bifocal lens consisting in polishing a portion of glass in. a single continuous surface, forming a mold .with a major portion having the complement of the curve desired on the distance vision of a bifocal and a central minor portion, having a different curve supporting the blank on the minor portion, subjecting the mold and blank to gradual heat to cause the blank to subside onto the mold, and restoring the polish on the mold engaging surface without altering the configuration produced by the heating effect. In testimony whereof I have afiixed my signature, in presence of two witnesses.

HARRY W. HILL.

Witnesses:

CHARtns I. KING, HARRY H. STYLL. 

